AP BIOLOGY

Detailed explanation-1: -Often, cells that are near one another communicate through the release of chemical messengers (ligands that can diffuse through the space between the cells). This type of signaling, in which cells communicate over relatively short distances, is known as paracrine signaling.

Detailed explanation-2: -Paracrine signaling acts on nearby cells, endocrine signaling uses the circulatory system to transport ligands, and autocrine signaling acts on the signaling cell. Signaling via gap junctions involves signaling molecules moving directly between adjacent cells.

Detailed explanation-3: -Direct Signaling Across Gap Junctions Gap junctions in animals and plasmodesmata in plants are connections between the plasma membranes of neighboring cells. These water-filled channels allow small signaling molecules, called intracellular mediators, to diffuse between the two cells.

Detailed explanation-4: -Answer and Explanation: Insulin signaling is an example of endocrine signaling. Insulin signaling is an important form of cell signaling for the maintenance of homeostatic blood sugar levels.

Detailed explanation-5: -In endocrine signaling, the signaling molecules (hormones) are secreted by specialized endocrine cells and carried through the circulation to act on target cells at distant body sites.